Electrostatic machine



Feb. 13, 1934. (1A. NlcKLE 1,947,220

ELECTROSTATIC MACHINE Filed March 2, 1932 Inventor": Clifford A. Nickle@224 His Attorney.

Patented Feb 13, 1934 UNITED STATES ELECTROSTATIC MACHINE Clifford A.Nickle, Schenectady, N. Y., assignor to General Electric Company, acorporation at New York Application March 2, 1932. Serial No. 596,18!

27 Claims. (Cl. 171429) My invention relates to electrostatic machines.

A source of high voltage of the order of 9. million volts is frequentlyrequired for electrical testing, or exciting electric. dischargedevices, such as X-ray tubes. The high voltage required for thesepurposes has generally been obtained heretofore by the use oftransformers, or induction coils. The large number of turns required inthe windings of these devices 'to obtain such high voltage, and thedifllculties involved in adequately insulating the windings makes theirconstruction expensive. Moreover, if the winding or winding insulationbreaks down electrically it is impracticable to repair it.

Electrostatic machines, on the other hand, are

of simple construction, but machines of this kind proposed heretoforefor producing high voltage have had too low current output for mostpur-.

the machine is so great that it is diillcult to construct the machine,and the floor space required for its installation would ordinarily makeits use. prohibitive.

In exciting the belt in a machine of this type the amount of charge thatcan be imparted to the belt is limited by the intensity of the electricfield of the exciting device and the portion of the belt movingtherefrom. In machines, as heretofore constructed, if the intensity ofthis field is increased to increase the charge on the belt, the airbetween the exciting device and the portion of the belt moving therefromwill become ionized, and. conducting, so that the electrical charge onthe belt will leak off to the exciting device, and in this way limit thecharge that can be imparted to the belt.

An object of my invention is to obtain a distribution of the electricfield between a belt, or other moving element, and the devices employedfor exciting it, which will permit a great increase in the electricalcharge that can be imparted to the belt, or moving element.

Another object of my invention is to provide an electrostatic machine ofthe endless belt type having a charge accumulating body arrangedentirely about the belt between its supports, so that the constructionof the machine will be simplilied.

Another object of my invention is to provide an electrostatic machineincluding a belt, a charge accumulating body associated therewith.

andlan improved belt exciting device for utilizing the charge carriedinto the body by the belt to electrically charge the belt movingtherefrom.

Another object of my invention is to provide a self-excited endless belttype of electrostatic mao0 chine having a belt supported on a roller andexcited, or charged, by friction between the belt and the roller, and anarrangement for stabilizing the operation of the machine. Furtherobjects and advantages of my inven- 05 tion will become apparent as thefollowing description proceeds, and the features of novelty whichcharacterized my invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

In the drawing, Fig. 1 is a diagrammatic perspective view of an endlessbelt type separately excited electrostatic machine embodying myinvention; Fig. 2 is an enlarged sectional view of the field pieces andcollector which are employed In for increasing the charge that canbe'imparted to the belt; Fig. 3 is a diagrammatic view partly in sectionof an endless belt type electrostatic machine similar to that shown inFig. 1, but of the self-excited type; Fig. 4 is a fragmentary view of aportion of a self-excited electrostatic machine, similar to that shownin Fig. 3, having an arrangement for stabilizing the operation of themachine, and Fig. 5 is a fragmentary view of an electrostatic machinelike that shown in Fig. 3 having an improved arrangement for separatelyexciting the machine.. 1

Referring to Fig. 1 of the drawing, the electrostatic machine which Ihave illustrated is of the separately excited type, and includes anendless belt, 1 of paper, or other suitable material, which is supportedin the form of an elongated loop on rollers 2 and 3. These rollers areadapted to be mounted in bearing supports, and the belt is driven byanelectric motor 4 suitably connected to the roller 2. A sphericalcharge accumulating body 5 is arranged about the belt-loop intermediatethe ends thereof, and is provided with openings'6 and 'I through whichthe belt-loop extends. The spherical body 5 is supported on aninsulating column 8 of sufiicient height to withstand the high voltageof the electric charge accumulated on the sphere. The insulatingbeltloop is made long enough to separate the rollers 2 and 3suillciently from the spherical body 5 to prevent any direct electricaldischarge, or leakage, from the sphereto the part 0 the constructionassociated with the rollers. he belt offers suflicient resistance to theflow of any charge on the sphere to prevent any substantial loss of 110charge therefrom. If desired, the spherical body may be charged toobtain several million volts and the voltage obtained depends upon thesize of the body and the general design of the machine. The high voltagecharge accumulated on the spherical body 5 may be withdrawn therefrom tosupply any suitable load for testing purposes, or exciting an electricdischarge device, such as an X-ray tube, in any convenient manner. Itwill be understood that this connection for withdrawing the charge fromthe spherical body 5 should be constructed in such manner as to avoidexcessive leakage of the charge into the surrounding air. This may beaccomplished by suitably connecting a sphere, which is insulated fromground, to the load device, and arranging this sphere in contact withthe spherical body 5. When the machine is utilized to excite an electricdischarge device, the charge may be supplied directly thereto bysupporting the device adjacent the spherical body 5.

In this construction, the portions of the belt loop moving from therollers 2 and 3 toward the spherical body 5 are electrically charged,and this charge is conveyed on these portions of the belt into thespherical body where it is collected and transferred to the outersurface of the body. In order to utilize fully substantially the entirelength of the belt-loop 1, I also electricallycharge the portions of thebelt-loop moving from the spherical body toward the rollers in such'manner as to increase the charge on the spherical body,

and remove this charge from the belt at the rollers.

The arrangement which I employ for charging the belt, may be used forcharging a moving charge conveying element of other types of machines.In the construction illustrated, the beltloop 1 is charged adjacent therollers 2 and 3, by a collector 9 and field pieces 11 and 12 which areconnected across a high voltage source of supply. The collector 9 isarranged adjacent the surface of the belt, and has a number of sharppoints 10 extending closely adjacent the surface of the belt across theentire width thereof, so as to facilitate the flow of an electricalcharge between the points and the belt. The field pieces 11 and 12 havea covering thereon, indicated at 13 and 14 in Fig. 2, which issemi-conducting. These field pieces are arranged adjacent opposite sidesof the belt 1 and adjacent the collector 9. The collector 9 and thefield pieces 11 and 12 may be'connected across a high voltage source ofsupply in any suitable manner to establish an electric field between thefield piecesand the collector. This electric field charges the I belt 1as it passes between the field pieces and towardthe spherical body 5. Asshown in Fig. 1, the field pieces 11 and 12 and the collectors 9 areconnected across a source of high voltage by grounding the collectorsand one terminal of a transformer T, and connecting the other terminalof the transformer to the field pieces through rectifying devices R. g

In an arrangement for exciting a belt in this manner the amount ofcharge which can be imparted to the belt is limited by the intensity ofthe electric field established between the exciting devices and thebelt. As the charge on the belt is increased, the intensity of thiselectric field is increased and when the intensity of this electricfield is great enough to ionize the air between the exciting devices andthe belt, the air becomes conducting, and the charge leaks off the beltto the'exciting devices. By providing electrically connected fieldpieces arranged on opposite sides of the belt adjacent the collector, Iobtain a distribution of the electric field between the exciting devicesand the belt, which will permit a large increase in the electricalcharge which can be imparted to the belt. In this way, I have alreadyobtained approximately sixty-six per cent increase in output of themachine, and theoretical considerations indicate that, by the use ofthis arrangement, I will be able to double the current output of themachine.

When the source of high voltage supply is connected across the collector9 and the field pieces 11 and 12, the belt will be charged in passingbetween the field pieces. If a direct electrical discharge takes placebetween the collector 9 and the field pieces 11 and 12, the belt 1 willno longer receive any charge, and .the supply of current to the loadwill be interrupted. When this direct electrical discharge occursbetween the collector 9 and the field piece 12 the belt will be punctured. In order to reduce the duration of any direct electricaldischarge in this way, I make the covering 13 and 14 on the field pieces11 and 12 of a semi-conducting material, such as a fabric impregnatedwith a phenolic resinous condensation product, varnished cambric, drywood, or

other ordinary insulating material having an insulating value comparablewith these materials.

I have found that this construction considerably .reduces the durationof any direct electrical discharge between the field pieces and thecollector. This is apparently dueto the'fact that as long as there is nodirect electrical discharge between the collector 9 and the field pieces11 and 12, the voltage on the outer surfaces of the covering on thefield pieces is substantially the same as that on the conducting coresthereof. As soon as the direct electrical discharge occurs, a surge ofcurrent takes place between the collector and the field pieces, and theresultant voltage drop across the semi-conducting covering on the fieldpieces greatly diminishes the difference in voltage between the outersurface of the field pieces and points of the collector, so as to stopthe fiow of current between the field pieces and the points of thecollector.

In order to convey to-the spherical body the electrical charge carriedinto the same by the belt, I provide collectors 15 and 16 inside of thesphere having a plurality of points extending in close proximity to thesurface of the belt and across the entire width thereof, which areconnected to the inside of the sphere as indicated at 17 and 18. It iswell known that the inside of a charge accumulating body of this-kind isat zero potential and that any charge conveyed into the same willimmediately fiow in any conducting path provided to the outer surface ofthe body.

The portion of the belt passing from the collectors l5 and 16 to therollers 2 and 3 is charged oppositely to the charge on the sphericalbody 5, so as to increase the charge thereon by arranging electricallyconnected field pieces 19, 20, 21 and 22 adjacent the belt and thecollectors 15 and 16. These field pieces are constructed like the fieldpieces 11 and 12 shown in Fig. 2, which. have been previously described.I prefer to utilize a portion of the charge carried into the sphericalbody 5 by the belt 1 for exciting these field pieces, and I accomplishthis by providing a collector 23 on the field piece 22, which extendsadjacent the inner surface of the belt. In this way a portion of thecharge carried into the spherical body 5 on the belt 1 passes to thefield pieces 19, 20, 21 and 22, and raises their potential sufficientlyto establish an electric field between the field pieces andthecollectors 15 and 16, so as to charge the portion of the belt passingfrom the collectors toward the rollers 2 and 3 oppositely to the chargeon the spherical body, and in this way increase the charge on thespherical body. The charge on the spherical body 5 is increased by thisarrangement because part of the charge carried on the belt 1 into thespherical body from adjacent the roller 2 passes to the collector 23 soas to raise the electrical potential of the electrically connected fieldpieces 19,

-20, 21, and 22 sufiiciently to establish an electric field between thefield pieces and their adjacent collectors l5 and 16. It will beunderstood that the charge on these field pieces is of the same sign asthe charge conveyed into the spherical body to'the' collector 23 on thebelt-loop 1. If the charge carried into the sphere from adjacent therollers 2 and 3 is positive, the collectors 15 and 16 will collect thispositive charge so that it passes to the spherical body 5. At the sametime a. portion of this positive charge will pass to the collector 23.and charge the field pieces 19, 20; 21, and 22 positively, and as thesepairs of field pieces are adjacent opposite sides of the upper and lowersides of the belt-loop 1, the portion of the belt passing fromthecollector 16 out of the sphere will be acted upon by the electricfield produced by the field pieces 19 and 20 so as to bind negativecharges to the belt 1 and repel positive charges from this portion ofthe belt so that they pass to the collector 16 and increase the chargeon the spherical body 5.

The portion of the belt-loop passing from the field pieces 19 and 20toward the roller 3 will therefore pass out of the spherical body 5 witha negative charge or a charge opposite to the charge on the sphericalbody 5. Similarly, the portion of the belt-loop 1 passing from-thecollectors 21 and 22 toward the roller 2 will be acted upon by theelectrical field established by the positively charged field pieces 21and 22 so as to bind the negative charge on the belt and repel thepositive charge so that it passes from the belt to the collector 15. Theportion of the belt-loop passing from the field pieces 21 and 22 towardroller 2 will also benegatively charged,v

so that the portions ,of the belt-loop 1 passing from the field pieces19 and 20 to the roller 3 and passing from the field pieces 21 and 22toward the roller 2 are utilized to increase the charge on the sphericalbody 5. If the charge conveyed into the spherical body 5 by the portionsof the belt-loop l passing from the rollers 2 and 3 toward the sphericalbody are negatively charged by an action similar to that abovedescribed, the portions of the belt-loop passing from the collectors 19and 20 to the roller 3 and passing from the field pieces 21 and 22toward the roller 2 will also be positively charged so that theseportions of the belt-loop will be utilized to increase the negativecharge on the spherical body 5. The electrical charge carried from thespherical body in this way is removed from the belt by the collector 9.

In Fig. 3 of the drawing, I have shown a selfexcited type ofelectrostatic machine similar to that shown in Fig. 1, and it alsoincludes an endless belt 1 supported in the form of an elongated loop onrollers 24 and 25, and a spherical charge accumulating body 5 isarranged about this beltloop intermediate the ends thereof. In thisconstruction, the charge carried into the spherical body on the belt 1from the rollers 24 and 25 is transferred to the spherical body, and thecharge carried into the spherical body on the belt is utilized to chargethe portion of the belt moving from the collectors toward the rollers 24and 25 oppositely to the charge on the spherical body to increase thecharge thereon, in the same manner that this is accomplished in the'ponstruction shown in Fig. 1. In this machine the roller 24 or 25 isdriven by a motor as for example an electric motor, and the belt iselectrified by the friction on hard rubber faces 26 and 27 of therollers. The rollers are also provided with conducting cores, which aregrounded at 28, 29. The friction between the hard rubber faces 26 and 27of the rollers and the belt binds the negative charge on the inside ofthe belt, and repels the positive charge to the outer surface of thebelt. In order to electrify the belt, interconnected grounded collectors30 and 31 are arranged ad- 'jacent the opposite ends of the belt-loopadjacent the surfaceof the belt, so that the positive charge is drawnfrom the belt to neutralize the outer surfaces of the belt and the beltthen passes from the rollers with a negative charge. The collectors 30and 31 also remove the charge from the belt which is carried from thespherical body to the rollers 24 and 25.

In a machine of this type the charge which can be imparted to the beltby the rollers is limited by the intensity of the electric fieldproduced between rollers and the portion of the belt moving from therollers toward the spherical body 5. When the intensity of this electricfield is increased above a certain value the air between the surface ofthe roller and this portion of this belt becomes conducting so that thecharge leaks off the belt to the roller. I have found that the amount ofcharge which can be imparted to the belt by the rollers can begreatly-increased by providing field pieces 32 and 33 adjacent theportion of the belt moving from the roller to the spherical bodyandhaving a surface which diverges from the outer surface of the belt. Itwill be noted, that in this construction the conducting core of theroller 24' and the field pieces 32, which are electrically connectedtogether through ground, distribute the electric field suddenlydecreases, and sometimes to zero, when the machine is in operation. Theoperation of the machine can be stabilized by arranging a collector 34closely adjacent the point where the portion of the belt moving towardthe roller 24 comes in contact therewith, and connecting this collector,as indicated at 35, to the conducting core of the roller 24. It will beunderstood, of course, that in modifying the machine in this way theroller 25 shown in Fig. 3 will alsobe provided 1 with a collectorarranged and connected as shown in Fig. 4.

The machine shown in Fig. 3 may. be separately excited, as shown in Fig.5'of the drawing, by arranging a collector 36 adjacent the point wherethe belt 1 moving toward the roller 24 initially 7 comes in contacttherewith, andconnecting this collector and the conducting core of theroller 24 across a high voltage source of supply. 'In this constructionthe collector and the conducting core of the roller are connected acrossthe secondary of a transformer T, by grounding the core of the roller at28 and one terminal of the transformer, and connecting the collector 36to the other terminal of the transformer through a rectifying device R.I

I have disclosed several embodiments of my invention, but I do notdesire to be limited to the particular arrangements set forth, and Iintend in the appended claims to cover all modifications which do notdepart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding both sides of said belt-loop intermediatethe ends thereof, means for driving said belt, and means utilizing bothends of said belt-loop for charging said body.

2. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding both sides of said belt loop intermediatethe ends thereof, means for driving said belt, and means utilizingsubstantially the entire length of said belt for charging said body.

3. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding both sides of said belt-loop intermediatethe ends thereof, means for driving said belt, means for electricallycharging the portions of the said belt-loop moving towards said body atboth ends of said belt-loop, and means within said body for transferringfrom said belt to said body the electrical charge carried from the endsof said belt-loop into said body.

4. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding both sides of said belt-loop intermediatethe ends thereof, means for driving said belt, means for electricallycharging the portions of said belt-loop moving toward said body at bothends of said belt-loop, means within said body for transferring fromsaid belt to said body the electrical charge carried from the ends ofsaid belt-loop into said body, and means within said body utilizing theportions of said belt passing from said body to the opposite ends of 4said belt-loop for increasing the electrical charge on said body. a

5. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding both sides of said belt-loop intermediatethe ends thereof, means for driving said belt, and means including acollector adloop moving toward said body, means within said body fortransferring the charge on said belt to said body, means within saidbody and including electrically connected field pieces arranged adjacentopposite sides of the portion of said belt moving out of said body forelectrically charging the outwardlymoving portion of said beltoppositely to the charge on the portion of said belt moving toward saidbody to increase the electrical charge on said body.

7. An electrostatic machine having an insulating belt, means forsupporting said belt in the form of an elongated loop, a chargeaccumulating body surrounding said belt-loop, means for driving saidbelt, means remote from said body for electically charging the portionof said beltloop moving toward said body, means within said body fortransferring the charge on said belt to said body, means within saidbody and including electrically connected field pieces arranged adjacentopposite sides of the portion of said belt moving out of said body forelectrically charging the outwardly moving portion of said beltoppositely to the charge on the portion of said belt moving toward saidbody to increase the electrical charge on said body, and means forelectrically charging said field pieces from said belt.

8. An electrostatic machine having a. moving element for conveying anelectrical charge, field pieces having a conducting core and asemi-conducting covering thereon and arranged adjacent opposite sides ofsaid eement, and means including an electrical connection between theconducting cores of said field pieces for electrically charging saidelement.

9. An electrostatic machine having a moving element for conveying anelectrical charge, a collector arranged adjacent said moving element,field pieces having a conducting core and a semiconducting coveringthereon and arranged adjacent opposite sides of said element, and meansfor electrically charging said element including a source of voltagesupply connected across said 12. ,An electrostatic machine having aninsulating belt, means for driving said belt, a collector adjacent saidbelt, field pieces electrically connected together and arranged adjacentopposite sides of said belt and said collector, and means including asource of voltage supply connected across said field pieces and saidcollector for charging said belt.

13. An electrostatic machine having an insulating belt, means fordriving said belt, and means for electrically charging said belt, saidmeans including a collector adjacent .said belt and field pieceselectrically connected together and arranged adjacent opposite sides ofsaid belt and said collector.

14. An electrostatic machine having an insulating belt, means fordriving said belt, a collector adjacent said belt, conducting fieldpieces lating belt,

between said roller and the electrically connected together and arrangedadjacent opposite sides of said belt and said collector, said fieldpieces having a semi-conducting covering thereon to reduce the durationof any direct electrical discharge between said field pieces and saidcollector, and means for establishing a difference in potential betweensaid collector and said field pieces to charge said belt.

15. An electrostatic machine having an insulating belt, means fordriving said belt, means including a roller engaging said belt forelectrically charging the same, and means for reducing the intensity ofthe electric field between the portion of said belt moving from saidroller and said roller to increase the electrical charge carryingcapacity of said belt, said means including a field piece adjacent theportion of said belt moving from said roller and having a surfacediverging from the surface of said belt in the direction of motionthereof.

16. An electrostatic machine having an insulating belt, means fordriving said belt, means including a roller engaging said belt forelectrically charging the same, and means including a field pieceadjacent the portion of said belt extending from said roller forreducing the intensity of the electric field between said roller and theportion of said belt extending therefrom to increase the electricalcharge carrying capacity of said belt.

17. An electrostatic machine having an insumeans for driving said belt,means including a roller engaging said belt for electrically chargingthe same by friction on said roller, and means including a field pieceadjacent the portion of said belt moving from said roller for reducingthe intensity of the electric field portion of said belt extendingtherefrom to increase the electrical charge carrying capacity of saidbelt.

18. An electrostatic machine having an insulating belt, means includinga roller having a conducting core and semi-conducting face engaging saidbelt for charging the same, means including a field piece adjacent theportion of said belt moving from said roller and electrically connectedto the core of said roller for reducing the intensity of the electricfield between the portion of said belt moving from said roller and saidroller so as to increase the electrical charge carrying capacity of saidbelt.

19. An electrostatic machine having an insulating belt, means includinga roller for supporting said belt and for electrifying the same byfriction on said roller, means for neutralizing a portion of said beltto charge the same, and means including a field piece adjacent theportion of said belt moving from said roller for reducing the intensityof the electric field between said roller and the portion of said beltextending therefrom so as to increase the electrical charge carryingcapacity of said belt.

20. An electrostatic machine having an insulating belt, means includinga roller having a conducting core and an insulating face for supportingsaid belt and for electrifying the same by friction on said roller, acollector adjacent the portion of said belt on said roller, meansincluding a connection between the conducting core of said roller andsaid collector for neutralizing a portion of said belt on said roller tocharge said belt, and means including a field piece connected to saidcollector and said conducting core and arranged adjacent the portion ofsaid belt moving from said roller for reducing the intensity of theelectrical field between said roller and the portion of said beltextending therefrom so as to increase the electrical charge carryingcapacity of said belt.

21. An electrostatic machine having an insulating belt, means includinga roller having a conducting core for supporting said belt and forelectrifying said belt by friction on said roller, a collector adjacentthe point where the portion of said belt moving toward said rollerinitially comes into contact therewith, and a connection between saidcollector and the core of said roller to stabilize the operation of saidmachine.

22. An electrostatic machine having an insulating belt, means includinga roller having a conducting core for supporting said belt and forelectrifying said belt by friction on said roller, a collector adjacentthe point where the portion of said belt moving toward said rollerinitially comes into contact therewith, a connectionbetween saidcollector and the core of said roller to stabilize the operation of saidmachine, and means for neutralizing a portion of said belt on saidroller to charge said belt.

23. An electrostatic machine having an insulating belt, means includinga roller having a conducting core for supporting said belt and forelectrifying said beltby friction on said roller, a collector adjacentthe point where the portion of said belt moving toward said rollerinitially comes into contact therewith, a connection between saidcollector and the core of said roller to stabilize the operation of saidmachine, means for neutralizing a portion of said belt on said roller tocharge said belt, and means including a field piece adjacent the portionof said belt moving from said roller for reducing the intensity of theelectric field between said roller and the portion of said belt movingtherefrom.

24. An electrostatic machine having an insulating belt, means includinga roller having an insulating face for supporting said belt, and meansfor establishing an electric field adjacent the point where the portionof said belt moving toward said roller initially comes into contacttherewith to electrify said belt.

25. An electrostatic machine having an insulating belt, means includinga roller having an insulating face for supporting said belt, means forestablishing an electric field adjacent the point where the portion ofsaid beltmoving toward said roller initially comes into contacttherewith toelectrify said belt, and means for neutralizing a portion ofsaid belt on said roller to charge said belt.

26. An electrostatic machine having an insulating belt, means includinga roller having an insulating face for supporting said belt, means forestablishing an electric field adjacent the point where the portion ofsaid belt moving toward said roller initially comes into contacttherewith to electrify said belt, means for neutralizing a portion ofsaid belt on said roller to charge said belt, and means including afield piece adjacent the portion of said belt moving from said rollerfor reducing the intensity of the electric field between said roller andthe portion of said belt moving therefrom.

27. An electrostatic machine having a paper belt, and means including aroller having a hard rubber face for supporting said belt and forelectrifying the same by friction on the face of said roller.

CLIFFORD A. NICKLE.

